1. Field of the Invention
The present invention relates to an ink-jet printer for ejecting ink droplets through a droplet outlet orifice (a nozzle) and recording on paper and an apparatus and a method of driving a recording head for an ink-jet printer.
2. Description of the Related Art
Ink-jet printers for ejecting ink droplets through a droplet outlet orifice communicating with an ink chamber and recording on paper have been widely used. Ink droplet ejection has been controlled as follows in such ink-jet printers of related-art.
FIG. 1 is a schematic diagram of a recording head and a drive circuit thereof in a related-art ink-jet printer. As shown, a recording head 500 includes a nozzle 501 and a piezoelectric element 502 provided in correspondence with the nozzle 501. The piezoelectric element 502 is fixed to a wall of an ink chamber (not shown) to which ink is supplied through an ink duct (not shown). A drive signal 504 of a specific waveform is selectively inputted to the piezoelectric element 502 through an on/ off switch 503. That is, the drive signal 504 is only inputted to the piezoelectric element 502 when the switch 503 is turned on. On the application of the drive signal 504, the piezoelectric element 502 is bent in such a direction that the ink chamber volume is reduced. An ink droplet is thereby ejected through the nozzle 501.
For such printers, one of the methods for producing halftone images is varying a droplet size dot by dot. In the drive circuit of the recording head of related art shown in FIG. 1, however, only one type of drive signal is inputted to the piezoelectric element 502 so that whether to perform ejection or not is only controlled. Consequently, it is impossible to perform control for varying a size of ejected droplet from droplet to droplet although the interval between recorded dots is controlled. It is therefore difficult to faithfully achieve various image representations such as more natural halftone images.